"That doesn't mean that just because someone comes into your house that you have the right to just shoot them,'' he said.
The same rules apply if a burglar's just escaped with your television set.
"You can't shoot him in the back if he's going out the door," said Mike Thompson, prosecuting attorney for Jefferson County, W.Va.
But it's a different matter if a person feels his or her life or the lives of others in the household are in danger.
"If a reasonable person perceives they are in fear of serious bodily injury or death or commission of a serious felony and it's a reasonable fear, they can protect themselves using deadly force," said Franklin County District Attorney Jack Nelson.
Section 505 of the Pennsylvania Crimes Code states that a person can use deadly force if it's necessary to protect themselves "against death, serious bodily injury, kidnapping or sexual intercourse compelled by force or threat."
Nelson is investigating last month's mobile home break-in in Chambersburg that resulted in the shooting death of one of the intruders.
Ernesto "Ernie" Casanova Jr., 17, was fatally shot by Daniel Alan Frazier, 18, during an April 23 break-in of Frazier's family's Sycamore Grove Road mobile home.
Six people have been charged in the break-in. One of the three who went into the mobile home was armed with a shotgun, according to charging documents.
Use of deadly force spelled out in Maryland and West Virginia laws are similar to Pennsylvania law.
The law in Maryland says if threatened with force, you are allowed to reply with force.
"If someone comes at you with a knife, you can respond with a gun,'' Salvatore said.
The same is true in West Virginia, where the view is that a homeowner may use deadly force to resist deadly force, Thompson said.
A February case in Chambersburg in which an intruder was fatally shot after forcibly entering a home was ruled a justifiable homicide.
At 6:45 a.m. on Feb. 16, William Barbour kicked in the front door of the home of his ex-girlfriend, Christine Pittman, and her boyfriend, P.J. Atkinson, who were sleeping in an upstairs bedroom.
Armed with a handgun, Atkinson fired multiple shots at Barbour as he advanced down the hallway, ultimately reaching and entering the bedroom. Barbour collapsed and died as he confronted Pittman.
"Mr. Barbour's death, tragic as it was, was a justifiable homicide," Nelson said. "P.J. Atkinson reasonably feared for his own safety and that of Christine Pittman at the time he used deadly force in an attempt to thwart Mr. Barbour's actions."
If threatened outside the home, the laws in all three states say you are obligated to retreat. That law doesn't apply when you're in your own home or place of work.
What happens when deadly force is used in break-in cases, and what makes them tough to prosecute, Thompson said, is that it depends almost entirely on what the victim perceived the situation to be at the time.
"It's his state of mind that's at issue," Thompson said. "It's all in the eyes of the beholder."
If deadly force is used, it's up to the jury to decide whether it's a case of self defense, he added.
If it's believed someone is breaking into your home, police say the homeowner should call for help first.
"First dial 911, then do whatever you feel is necessary to protect yourself," said Sgt. Patrick Madigan of Pennsylvania State Police.
But protecting yourself doesn't mean getting a gun and start shooting, he added.
In most break-ins, the thieves are there to steal property, not to harm anyone, he said.
"Property can be replaced. It's not worth getting shot or harmed or worth shooting someone," Madigan said.
In all three states, a homeowner is allowed to have legal weapons in the home. There are laws that govern purchase and possession of such weapons.